Fouling of heat transfer surfaces of petroleum processing equipment occurs continuously during the period when petroleum or its derivatives are being processed in the equipment. The fouling is caused by the gradual buildup of a layer of high molecular weight polymeric material resulting from the thermal polymerization of unsaturated materials which are present in the petroleum. As time goes by, fouling continues with the attendant loss of heat transfer until finally the point is reached where it becomes necessary to take the equipment out of service for cleaning. Cleaning is expensive and time consuming, consequently methods of preventing fouling, or at least significantly reducing the rate of fouling, are constantly being sought.
The most economical method of reducing the fouling rate in process heat transfer equipment is to add chemicals which inhibit fouling, called "antifoulants", to the feed stream being processed. Many antifoulants are not satisfactory for use with high sulfur-containing hydrocarbons because of the formation of undesirable side products.